Sunday, 7 October 2012

If God exists, he exists necessarily

John said something to the effect that if God exists, He exists necessarily, but that doesn't prove He exists. I didn't take time to ask John about that statement at the conference, but I am wondering what it meant. I would have thought that if we know that any entity exists necessarily, that is proof that the entity exists. How can a being that exists necessarily, fail to exist?

I would have thought that we don't know that God exists necessarily. In fact, although I do believe in the actual existence of God, I don't see any way in which it would be incoherent or logically inconsistent if God did not exist, so for me it seems very hard to imagine that God necessarily exists.

Maybe the idea is that even though there are, I think, almost certainly logically possible worlds in which God does not exist, there is a narrower subcategory of possible worlds, in all of which God exists, and then one can define some sort of `necessity' in a weaker sense than logical necessity as applying to all those logically possible worlds in the subcategory, so that with this restricted meaning God `necessarily' exists. This would be rather in the same way as we can define a subcategory of possible worlds in which all physical universes within each such world would obey Maxwell's equations. Then within all such restricted worlds, charge is `necessarily' conserved, even though there are other logically possible worlds with charge, but without Maxwell's equations or some other equations implying the conservation of charge, in which charge is not conserved, so that relative to all logically possible worlds, charge is not necessarily conserved. But these stronger meanings of necessity, restricted to smaller subcategories of worlds than the entire set of logically possible worlds and yet to broader subcategories than just the one actual existing world (all that actually exists, so that it is just one world even if it includes God, a multiverse, and other existing entities), seem to me rather ad hoc. I can understand statements applying to our actual world, such as `God exists,' and I can understand statements applying to all logically possible worlds, such as `Given the axioms of arithmetic, 1+1=2,' but I find it hard to understand statements about vague classes of worlds larger than the one actual world but smaller than all logically possible worlds.
John's Response: In saying that God exists 'necessarily', theologians do not mean because of some external logical necessity but because of the internal divine fact that God who has being in himself does not depend for existence on any other entity. The medieval theologians called this property 'aseity'. So if there is a God, his existence required no further explanation, but it does not follow that there has to be a God possessing aseity.

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